Category Archives: The basics

Sugar

This is our first of two contributions to Advent Botany 2015.

Sugar plums dance, sugar cookies disappear from Santa’s plate, and candied fruit cake gets passed around and around. Crystals of sugar twinkle in the Christmas lights, like scintillas of sunshine on the darkest day of the year. Katherine and Jeanne explore the many plant sources of sugar.

Even at a chemical level, there is something magical and awe-inspiring about sugar. Plants – those silent, gentle creatures – have the power to harness air and water and the fleeting light energy of a giant fireball 93 million miles away to forge sugar, among the most versatile compounds on earth, and a fuel used by essentially all living organisms.

Sugar naturally occurs in various chemical forms, all arising from fundamental 3-carbon components made inside the cells of green photosynthetic tissue. In plant cells, these components are exported from the chloroplasts into the cytoplasm, where they are exposed to a series of enzymes that remodel them into versions of glucose and fructose (both 6-carbon monosaccharides). One molecule of glucose and one of fructose are then joined to form sucrose (a 12-carbon disaccharide). See figure 1.

Sugars: glu, fru, and sucrose

Figure 1.

Sucrose is what we generally use as table sugar, and it is the form of sugar that a plant loads into its veins and transports throughout its body to be stored or used by growing tissues. When the sucrose reaches other organs, it may be broken back down into glucose and fructose, converted to other sugars, or combined into larger storage or structural molecules, depending on its use in that particular plant part and species. Since we extract sugar from various parts and species, the kind of sugar we harvest from a plant, and how much processing is required, obviously reflects the plant’s own use of the sugar. Continue reading

How giant pumpkins got so big: A Q&A with Jessica Savage

Biologist Jessica Savage answers a few of our questions about her research on the physiology behind giant pumpkin size.

In October 2014, a giant pumpkin grown by Beni Meier of Switzerland tipped the scales at 1056 kilograms (2323 pounds) and set a new world record for the heaviest pumpkin ever weighed. Modern competitive pumpkin growers have been imposing very strong selection on pumpkin size for decades. Pumpkin fruit size keeps climbing, and old records are broken every year or two (Savage et al. 2015).

Beni Meier with his 2014 record-winning 2323-pound pumpkin, presumably a specimen of the Atlantic Giant variety of Cucurbita maxima. Photo from here.

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Triple threat watermelon

Will seedless watermelons make us superhuman or turn our children into giants?  Hardly, but they do give home cooks the power to count chromosomes without a microscope.   Just a knife or a hard thunk on the sidewalk are enough to get a watermelon to spill its genetic guts.

If you were reading a Hearst Corporation newspaper in late 1937, you might have thought humanity would eventually be swallowed up by giant carnivorous plants, unwittingly unleashed by uncontrolled biotechnology.  The San Francisco Examiner reported on November 21st of that year that the discovery of an “elixir of growth,” meant that “…science may at last have a grip on the steering wheel of evolution, and be able to produce at will almost any kind of species…”  including “…a plague of man-eating ones.”  In 1937 Americans had much more important things to worry about, just as we do now.  Still, that discovery may in fact have threatened one cherished aspect of the American way of life by triggering the slow demise of late summer state fair watermelon seed spitting contests.  It doubtlessly paved the way for seedless watermelons, and in 2014 the total harvest of seedless watermelons on American farms – nearly 700 thousand tons – outweighed the seeded watermelon harvest more than 13 to 1 (USDA National Watermelon Report). A similar pattern is emerging this year.  Is there no stopping the attack of the seedless watermelons?

Image from microfilm of an actual page in the San Francisco Examiner, published Sunday November 21, 1937. Found in the Media and Microtext Center of Stanford University Libraries.

CLICK to read. Image from microfilm of an actual page in the San Francisco Examiner, published Sunday November 21, 1937. Found in the Media and Microtext Center of Stanford University Libraries.

And more important, how is it even possible to get seedless fruit from an annual plant?  From a plant whose only mode of reproduction is through those very seeds?  From a plant that cannot make suckers as bananas do and cannot be perpetuated endlessly through grafts like fruit trees and vines?   Such is the challenge posed every single year by watermelons, but thanks to the “elixir of growth” discovered by Albert Blakeslee and subsequent work by Hitoshi Kihara, one of the most prominent agricultural geneticists of the 20th century, the world has an elegant solution. Breeders continually improve the varieties available, and consumer demand keeps growing, yet seedless watermelon production methods have remained essentially unchanged for three quarters of a century. Continue reading

The new apples: an explosion of crisp pink honey sweet snow white candy crunch

What’s in a name?  An apple with an old fashioned name could taste as sweet, but it might not sell.  The most sought after branded varieties reveal what people look for in an apple: sweet and crunchy and bright white inside.  Do the fruits live up to their names?  Are Honeycrisp apples crunchier than others?  Do Arctics actually stay white?  We zoom in on the cells to find out.

Some of you will remember the era when the Superbowl halftime show repeatedly featured Up With People.  That was around the time when Granny Smiths arrived in our supermarkets and finally gave Americans a third apple, a tart and crunchy alternative to red and golden delicious.  Those were simple days.  Continue reading

Apples: the ultimate everyday accessory

Infinity scarves? No. They won’t keep doctors away. Apples are the ultimate everyday accessory (fruit). Katherine explains where the star in the apple comes from. Could it be due to a random doubling of chromosomes? We also give readers the chance to test their apple knowledge with a video quiz.

Although apples are not particularly American – nor is apple pie – they color our landscape from New York City to Washington State, all thanks to Johnny Appleseed. Or so goes the legend. Everyone already knows a lot about apples, and for those wanting more, there are many engaging and beautifully written stories of their cultural history, diversity, and uses. See the reference list below for some good ones. There is no way I could cover the same ground, so instead I’ll keep this post short and sweet (or crisp and tart) by focusing on apple fruit structure and some interesting new studies that shed light on it.
Of course if you do want to learn more about apple history but have only 5 minutes, or if you want to test your current knowledge, take our video quiz! It’s at the bottom of this page. Continue reading

Walnut nostalgia

Walnuts may not seem like summer fruits, but they are – as long as you have the right recipe.  Katherine takes you to the heart of French walnut country for green walnut season.

France 1154 Eng newAnnotation fullRes 2

Public domain, via wikimedia commons

English walnuts do not come from England. The English walnut came to American shores from England, but the English got them from the French. The (now) French adopted walnut cultivation from the Romans two millennia ago, back when they were still citizens of Gallia Aquitania. Some people call this common walnut species “Persian walnut,” a slightly better name, as it does seem to have evolved originally somewhere east of the Mediterranean. But the most accurate name for the common walnut is Juglans regia, which means something like “Jove’s kingly nuts.” I think of them as queenly nuts, in honor of Eleanor of Aquitaine, because if any queen had nuts, she certainly did. During her lifetime the Aquitaine region of France became a major exporter of walnuts and walnut oil to northern Europe, and it remains so more than 800 years later. Continue reading

Going bananas

What can make me feel less guilty about buying bananas? Science.

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Trying to get the banana back in the peel

I am genuinely curious about the size of the fraction of carbon in my two-year-old that is derived from bananas. When we have bananas in the house, which is most of the time, she eats at least part of one every day. She loves them peeled, in smoothies, dried, in banana bread, or in these banana-rich cookies, which sound like they shouldn’t be good but are totally amazing. Bananas are inexpensive and delicious, and making nutritious food with them gives me a sense of parental accomplishment. Nonetheless, always I feel a niggling sense of guilt whenever I plunk a bunch of bananas into the shopping cart. Prosaic though it may be, most of this is contrition inspired by the “local food” movement. I know that very little is benign about the process responsible for bringing these highly perishable tropical fruits to my table for less than a dollar a pound. The remainder of my remorse is conviction that bananas should not be taken for granted. Not only is banana history and biology interesting, but the banana variety in our grocery stores, the Cavendish, is in danger of commercial extinction. There isn’t an easy solution to the problem or an obvious candidate for a replacement variety. The history of the Cavendish’s rise, and the biology behind its current peril, makes for a good story. Continue reading

Origin stories: spices from the lowest branches of the tree

Why do so many rich tropical spices come from a few basal branches of the plant evolutionary tree?  Katherine looks to their ancestral roots and finds a cake recipe for the mesozoic diet.

I think it was the Basal Angiosperm Cake that established our friendship a decade ago.  Jeanne was the only student in my plant taxonomy class to appreciate the phylogeny-based cake I had made to mark the birthday of my co-teacher and colleague, Will Cornwell.  Although I am genuinely fond of Will, I confess to using his birthday as an excuse to play around with ingredients derived from the lowermost branches of the flowering plant evolutionary tree. The recipe wasn’t even pure, since I abandoned the phylogenetically apt avocado for a crowd-pleasing evolutionary new-comer, chocolate.  It also included flour and sugar, both monocots.  As flawed as it was, the cake episode showed that Jeanne and I share some unusual intellectual character states – synapomorphies of the brain – and it launched our botanical collaborations.

Branches at the base of the angiosperm tree
The basal angiosperms (broadly construed) are the groups that diverged from the rest of the flowering plants (angiosperms) relatively early in their evolution.  They give us the highly aromatic spices that inspired my cake – star anise, black pepper, bay leaf, cinnamon, and nutmeg.  They also include water lilies and some familiar tree species – magnolias, tulip tree (Liriodendron), bay laurels, avocado, pawpaw (Asimina), and sassafras. Continue reading

Let’s get it started with some black-eyed peas (and rice)

You don’t have to be superstitious to believe in the power of hoppin’ john on New Year’s Day.  Katherine’s recipe is below, but first, she takes this good excuse to talk about the structure of beans, the magical fruit (really seeds).

The magic of beans
Beans are extremely satisfying seeds.  They are large and germinate easily.  They can be harvested young and eaten soft – like limas, favas, and green peas – or in their fresh pods, like green beans and sugar snap peas.  They are most beautiful and useful when allowed to mature and dry naturally.  They are creamy white, chestnut, blue-black, or pink; mottled, speckled, cow-spotted, or black-eyed; fat and reniform, or shaped like a lens or a ram’s head.  They can weigh down pie crusts or fill bean bags.  Food co-ops everywhere are built on the cornerstones of bulk bins full of colorful dried beans.  Running your hands through a bowl of cool dried beans is an inexplicably simple joy. Continue reading

The irrational nature of pie

What is a nut, and why is the answer so convoluted? For Thanksgiving, Katherine explores pecans and the very best vegetarian turkey substitute ever: pecan pie.

Traditions
Thanksgiving is all about tradition, and wherever there is tradition, there are entrenched ideas about the right way to do things. Strong opinions can breed discord, judgmental grumbling, or silent rants about how people with so little sense cannot possibly be blood kin or their freely chosen companions. So much for the theory of mind we all developed as toddlers. And so it goes with my feelings about pecan pie.

Pecan pie is properly made according to the recipe on the Karo syrup bottle, preferably by my own father. The recipe does not include bourbon. To be clear, I love bourbon. Bourbon is our only indigenous whiskey. It is made of corn and aged in American oak. I love bourbon, and I respect it enough to drink it neat, from a glass, alongside my pie.

We can all agree that pecan pie should not be rolled in molasses, breaded with crushed pork rinds, and deep fried. Some reasonable people, however, do add chocolate. It might taste just fine that way – even delicious – but it disqualifies the resulting pie from the category under discussion. Sneaking it in under another name doesn’t work either. When the good bourbon-loving people of Kentucky add chocolate to a pecan pie and call it Derby pie, not only are they infringing on a trademark, they are using the wrong kind of nut. Derby-Pie ® is made with walnuts. There is therefore still no excuse for adulterating good pecan pie with chocolate.

What is a pecan?
A pecan half is a rich fat-filled embryonic leaf (a cotyledon) from a pecan tree seed. The flat side of a pecan half bears a pale shield-shaped scar where it was joined to the other cotyledon and where a tiny knobby embryonic root sits waiting for the chance to grow out and start drawing up water. Each pecan half is wrinkled like a brain hemisphere, crammed into its shell. In the natural world, when conditions are right for germination, a pecan seed imbibes water and its cotyledons swell enough to crack open the shell. The cotyledons provide an extremely calorie-dense sack lunch for the seedling to draw upon until it develops leaves and starts photosynthesizing food on its own. Continue reading